cetoole

Got my NAD RP18 today from Fungi. Gonna have to wait for the boss to go to lunch though to give them a spin, but he is right, you basically have to be a leprechaun to wear these properly.

http://www.modu.it/CARATTERISICHE_TERMICHE_DISS.pdf

Ask. It is amazing what can be done with email on this internets thing today. Besides, Tyll and his peeps havnt bitten anyone lately (or if they did, there were no complaints).

Sweet, thanks Marc, a schematic would be perfect.

Anyone ever modify a SRM-1/mk2 for 620v bias, or even sketch out a schematic for the stock bias supply?

Looks like a pretty sweet amp, great gift. There are some things you could try to get rid of the hum, such as increasing the power supply filtering, but just casually looking at it, it would seem your friend used a reasonable amount of capacitance in the supply. No idea how many poles he has on the filter, but maybe he would be the better person to ask. Do you have any sort of schematic that this amp was built to follow? The other issue could be emi from the transformers, especially since it looks like the one toroid is pretty solidly over part of the audio circuit. Is the hum the same in both channels?

I like my QP400, great headphones for the $35 I paid. I would put them around the HD600 level generally, better for some things and worse for others. Definitely not as good as any of my 'stats though, but good enough to stick around. Sounds like they have a treble spike moderate in amplitude, but covering a relatively narrow range, which makes it rather dependent on the music I am listening to if this bothers me or not. Havnt heard any of the other Quarts though, so no idea if this is a family trait. You are right though, they are pretty damn comfy. Hard to drive for normal dynamics, but not even close to any of my orthos, and definitely not like my piezo.

I think its 8x PCM1704, but cant quite see well enough. Its a crazy amount of parts though, and whats with all the parts being through hole, or the hookup wire for the spdif inputs?

20 hours is assuming there is absolutely nothing currently in the battery, and of course, this is unrealistic. I would have to look up battery curves, but all batteries drop voltage as they discharge, and you get into distortion once this voltage gets too low. There could still be plenty of power left in the battery; it just isnt usable for us. Overnight is the general rule of thumb people go by for this amp. Glad you found some suitable wallwarts, just make sure the polarity is correct.

AMB has three suitable wallwarts posted on his website that you can order. No idea about B&M store availability. I actually had two or three suitable ones just laying around at home when I built one for my boss. As for the battery charge time, it depends on the state of discharge. The onboard charger is a constant current arrangement that charges the battery at 16mA by default. It will take quite some time to charge, potentially up to about 20 hours.

I get full volume out of the ESP/950 using either the E/90 or the SRM-1/mk2 about a second after I hit the power switch.

Just dont leave it plugged in constantly Smeggy. It is possible to overcharge the battery in this, as it is just a constant current trickle charger. By constantly, I mean days at a time, one workday isnt a problem.

What was wrong with it? Also, did you mod it in any way?

Nope, no internal digital filter. Its just a good old (sorta) R2R DAC, with some internal tricks. You can run it at 16/44.1 no problem, if thats what makes you hot. Of course, I would advocate using a good digital filter with it, like the SM5847.

In for parts am I.

Its not nearly that simple. The reason Async USB is (practially) immune to jitter is because it contains the master clock and requests more data from the computer to keep it's buffer partially full. The computer's clock is slaved to the DAC clock, and all incoming data is buffered and reclocked by the DAC clock. You can modify a SPDIF source to act like this, though it adds a second wire to the interface and is completely nonstandard, so you wont see it in commerical devices, except for Lessloss, I believe. To keep SPDIF jitter down would require a completely separate reclocking system from the USB.

I doubt it, and I think I see a standard power cable coming out of the rear on the first pic posted here. I have no more information on this than anyone though. I do think I remember hearing that CH likes current mirror based I/V converters though, but this could be old data, and I dont even know that they use a current out DAC. The Ayre D-1 does (4x PCM1704) as does the CX-7 (PCM1738), but who knows? Gordon mentions IV discrete, and he would certainly know the difference, but as he doesnt know what DAC is used, I guess this could be an assumption on his part.

My guess, based off what I know about Ayre, is that they didnt include SPDIF input because of worries about jitter on that interface. I have read that they havnt made an outboard DAC before for this reason alone. Async USB basically solves the jitter problem for them, as the only jitter which should be present is the intrinsic jitter of the fixed XO they use to clock it and the jitter added on the board by parts like the FPGA (which will be handling the oversampling), but I wouldnt be surprised to find they are reclocking between the FPGA and DAC(s). You can make a SPDIF interface with very low jitter with the application of a good secondary PLL reclocking the incoming data, either in analog with a VCXO or digital with FIFO buffering, but neither of these solutions are very simple or cheap. I am sure Ayre has people who could easily handle it, but suspect it was omitted because they were trying to meet a price point.

Nope, havnt even opened it up, or even looked for the screws to get it apart. Honestly, I havnt felt the need to, as it is sonically nearly perfect for me, at least for the time being. So, how is it damped stock, and does removing some of it add any harshness? I could maybe do with just a tiny tilt in FR, as it is a hair dark at times, but it really doesnt bother me. The cable is crap and will have to go, but this is as much because it is short and requires an adapter for any amp besides the stock as anything. I have lightly stuffed the rear of the pads with some felt, about 4mm total, which gets the stator, or the shield in front of it, off my ear. Stock it pushes against the upper cartilage part of my ear and becomes uncomfortable after a fairly short period of time. I still touch, but there is absolutely no pressure, and I can wear them all day. I do wish that the pads were nicer, something in leather with a bit better stuffing, maybe lightly shaped.

Indeed. Certainly my first choice of current production DACs.

Never tried the 600 or 120ohm versions, didnt even know they came in 120ohm. Senns would probably be a decent choice for the OP to try. Personally, I love the ESP/950 bass for metal more than any other headphone I have owned or borrowed.

What do you mean by "NOS DAC chip"? There are plenty of DACs with no internal upsampling/oversampling that can support higher than 20/44.1. The PCM1704 is probably the best example of this, and IMO, still the most interesting current production DAC out there.

That sounds like a pretty horrible idea to me, at least if you are referring to the Pro 770-80. These have got to be one of the worst sounding headphones I have ever tried. Never heard the 990 though, but looking at Headroom's graphs, I wont be going out of my way to hear it anytime soon, considering my taste in music. Every time I have heard the 880 it wasnt bloody aweful like the 770, but was a signature that I never enjoyed, especially with the brightness. The HD580/600 kept me happy for several years though, but I am favoring the planar sound more theses days.

I am not surprised that the superglue didnt work, I have never had any luck with it for something like this. Too brittle and it hasnt ever done a good job in bonding small metal surfaces for me. Much better for closing cuts though. If I understand where the screws are correctly, it doesnt look like replacing the arc assembly will replace the damage you have done, as it looks like the screws are on the earcup assembly, not the arc assembly. Good luck though in getting this all replaced. The Lambda Pro sound is starting to get on my nerves. There is something wrong and slightly unpleasant sounding to me in the upper mids and the bass sort of sucks. It does really nothing for me that would give it a permanent place in my collection, even though it is probably about my second favorite overall. I much prefer the ESP950 at this point, by a very large margin in every respect. Tried the Koss out of the SRM-1/mk2 over the weekend, and it sounds pretty good. A bit darker and a bit smoother to my ears than the stock E/90.